Hey mate, whereabouts are you? I'm in SA & I've recently put my R34 GT-T on car sales.com. It's the white one with LOADED plates. It's got the factory nismo kit, tint, xenons and pretty much all the mods u were after. Running standard turbo with standard boost (around 9psi due to where the actuator hose has been plugged. Also has full trust FMIC kit, HKS suspension, 18 x 10 MAD CST rims, huge stereo blah blah etc etc go have a squiz. Take 21,000 (firm).
If your not interested I can still help u with advice. Firstly, it's best to find something with low kms. Remember they need a major service at 100k that'll set u back close to a grand (inc. labour). Try to find something that hasn't been boosted. Once you start boosting standard turbos up past 12psi their lifespan tends to suffer (and you never know how much of a caning the thing has taken). Anything over 200kw at the wheels and you'll be wanting to do a fuel pump, and an "FC" (or something even snazzier like a haltech) is always a good idea, especially when not running standard boost. You can get around these things by f**king around with your fuel pressure regulator, but the versatility offered by an aftermarket ECU is vital for any serious performance gains.
Next stage up and you have to do injectors & start looking at bigger turbo kits. Labour is the main killer, so if you're keen on (and capable of) doing work yourself you can literally save a FORTUNE! The only thing you really have to outsource is the tune. Simon at Morpower is a God if you're local.
As for prices, a lot of guys on here sell great 2nd hand stuff so keep your eyes peeled for bargains. NEW and for the good stuff, prices will look something like this:
Injectors (NEO R34 motors have top feed siemens type making choice more restricted). Nismo make 480s (God knows why), Blitz make 525s, Power Enterprises do a set of 650s and there are a few more even bigger. You can pay up to $1,200 for a set, but anyting under a grand is good for brand name newbys. Ebay are doing quite a few cheapies (run an international search) but I can't comment on the quality.
Power FC: hard to find a 2nd handy for a 34, but if you can, don't pay anymore than a grand. New with commander they'll set u back $1,500-$1,700. When doing an ECU change, it's worth upgrading your AFM (if you still need one) to a Z32 model. New these are bullshit but you can get a 2nd handy for around $200 with plug (don't forget to change your AFM selection on your hand-controller if running an FC).
Fuel pump: Bosch are well priced but you'll have to do a bit of fiddling around when fitting them. Nismo do one that comes complete with cradle / pick-up etc for $595. It literally slots straight in and is good for 400rwkw. Boost controllers (cheap with a T-piece but they're dodgey) you can get 2nd hand for a coupla hundred.
Last stop (aside from getting an aftermarket boost guage) is turbo / manifold / wastegate choice. The list is endless, but if you go much bigger than standard expect the car to get laggier. Price can vary immensely. Nothing beats HKS, but they're not cheap Example: HKS 2835 GT Pro with above mods will give you around 250rwkw @ 1.5bar. Enough to embarrass most things on the road. Much bigger and you'll start taking off like a snail (but nothing feels better than coming on boost and sling-shotting past someone like they're standing still)!! Anything decent will cost u at least a couple of grand, but there are always bargains floating around!
Hope this helps